Similarly …show more content…
Structure D’s conformation required the greatest energy overall. Structures A and B, structures C and D, and structures E and F are diastereomers of each other. The cis structure of each pair seems to require greater energy for all pairs. The energy differences between structures A and B is about ∆6kj/mol, structures C and D have energy differences of about ∆20kj/mol and structures E and F, ∆15 kj/mol. Structure A, compared to B, had less energy because the R group is in equatorial, the same for structures E, in the among the E and F …show more content…
Since structure D had all substituents in axial position, this position is least stable. Structural E, had all substituents in equatorial position, which is more energetically favorable because there is less steric strain. Steric strain is when there is repulsion between the electron clouds of the groups or atoms. This arises, especially in structure D, when the hydrogens attached in the axial methyl substituents interact with one another. For cyclohexanes it is best when any of the substituents lie in equatorial position as much as possible, because it gives way to less steric strain. When the cyclohexanes are poly-substituted, not all the isomers can occupy all equatorial positions, yet the most stable isomer will have substituents in equatorial positions. The trans isomers, compared to the cis isomers have the greatest energy. Structures C and F’s cis isomers are less thermodynamically stable than their trans. The cis and trans isomer are not the same isomer in different structural conformations, and nor are they able to readily convert by rotating them. The bonds will have to be broken for this to